This invention relates to geothermal wellheads and to packing assemblies positioned inside the wellhead to seal between the wellhead and an inner wellhead casing as the casing moves up and down in response to changes in thermal conditions in the wellhead. U.S. Pat. No. 3,976,130, issued Aug. 24, 1976, and assigned to the same assignee as the present application, describes packing means for a geothermal wellhead assembly by which a seal is effected between a casing and a bore within the wellhead, the seal being maintained throughout longitudinal movement of the casing in response to temperature changes within the wellhead. While the packing means described in the above noted patent does produce an effective seal, further study revealed the need for a packing assembly which was not as difficult to install, could be used with a number of casing expansion programs and permitted the use of different types and configurations of seals.